get_posts wont produce a list of custom type from a given category [duplicate]

I’m assuming ‘news_category’ is a custom taxonomy; if not, and if you have simply created a new post category called ‘news_category’, it will only work if you add support to your custom post type. Be aware though that this will add complexities to your feeds and queries, as well as affecting how category posts show in the admin. It is most straightforward to do this with a custom taxonomy if you can.

Onto solving this using a custom taxonomy:
You need to add a taxonomy query to your arguments, so WP knows where to look for that new term.

$news = get_posts(
    array(
        'post_type' => 'news',
        'tax_query' => array(
            array(
                'taxonomy' => 'nameofyourcustomtaxonomy',
                'field'    => 'slug',
                'terms'    => 'news_category',
            ),
        )
    )
);